capture_image

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden. It discloses that this is a read-only operation (screenshot capture) rather than a mutation, and specifies the PNG output format. It doesn't mention any side effects (e.g., whether navigation occurs), but the 'current page' phrasing reasonably implies no navigation. The description adds meaningful context beyond what's absent in annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single clear sentence plus a compact JSDoc return comment. It's appropriately minimal with no wasted words. Front-loaded with the action verb. Could arguably add a bit more behavioral detail, but for the content it delivers, it's efficient.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

This is a relatively simple single-parameter tool with a clear return type (PNG). The description covers the essential purpose and output format. However, it lacks context about the agent concept (the index parameter suggests a multi-agent environment whose behavior isn't explained) and any usage caveats. For such a simple tool, it's adequate but could clarify the agent-index dimension.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the single parameter 'index' is fully documented in the schema as 'One-based agent index.' The description's @return JSDoc annotation adds the PNG format context, which is useful. However, the description doesn't explain why an 'index' is needed for a screenshot or what the index refers to beyond the schema's single line.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action: capture a PNG screenshot of the current page. The verb 'capture' plus the resource 'PNG screenshot of the current page' gives a specific, actionable purpose. It doesn't differentiate from siblings, but none of the sibling names appear to be screenshot-related, so confusion risk is low.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance on when to use this tool, when not to, or prerequisites. For instance, the page must be loaded/active for a meaningful screenshot, but this isn't stated. No alternatives are named or excluded. The only implicit context is that it captures the 'current page,' implying some navigation must have occurred first.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.